I'm on windows 8 and couldn't get Putty to work either but i did with using the Arduino IDE:
and following the helpful instructions here:
and here:
basically select newline in the drop down menu before you type in teh SSID and click enter.
I found though that in order to connect to the cores after i got them to work via USB was to go into the app, let it to try and connect to them and then click back in the top left, it loaded tinker and i could see the cores. But thats on Android, can't imagine its too different on iOS.